RPE 1.2.1 comes with a brand new Info Center: http://pic.dhe.ibm.com/infocenter/rpehelp/v1r2m1/index.jsp?re=1&topic=/com.ibm.rational.pe.nav.doc/helpindex_rpe.html&scope=null
The 1.2 version of the Info Center is still available and is valid but it applies to RPE 1.2 and 1.2.0.1 and only contains information relevant to those RPE versions. And similarly the 1.1 version Info center is still available.
Please update your bookmarks and make sure you use the Info center version matching your RPE release.